PhotoluminescencePhotoluminescence (abbreviated as PL) is light emission from any form of matter after the absorption of photons (electromagnetic radiation). It is one of many forms of luminescence (light emission) and is initiated by photoexcitation (i.e. photons that excite electrons to a higher energy level in an atom), hence the prefix photo-. Following excitation, various relaxation processes typically occur in which other photons are re-radiated.
Free contentFree content, libre content, libre information, or free information, is any kind of functional work, work of art, or other creative content that meets the definition of a free cultural work, meaning "works or expressions which can be freely studied, applied, copied and/or modified, by anyone, for any purpose." A free cultural work is, according to the definition of Free Cultural Works, one that has no significant legal restriction on people's freedom to: use the content and benefit from using it, study the content and apply what is learned, make and distribute copies of the content, change and improve the content and distribute these derivative works.
Spatial resolutionIn physics and geosciences, the term spatial resolution refers to distance between independent measurements, or the physical dimension that represents a pixel of the image. While in some instruments, like cameras and telescopes, spatial resolution is directly connected to angular resolution, other instruments, like synthetic aperture radar or a network of weather stations, produce data whose spatial sampling layout is more related to the Earth's surface, such as in remote sensing and .
Image resolutionImage resolution is the level of detail an holds. The term applies to digital images, film images, and other types of images. "Higher resolution" means more image detail. Image resolution can be measured in various ways. Resolution quantifies how close lines can be to each other and still be visibly resolved. Resolution units can be tied to physical sizes (e.g. lines per mm, lines per inch), to the overall size of a picture (lines per picture height, also known simply as lines, TV lines, or TVL), or to angular subtense.
Wikimedia CommonsWikimedia Commons (or simply Commons) is a media repository of free-to-use images, sounds, videos and other media. It is a project of the Wikimedia Foundation. Files from Wikimedia Commons can be used across all of the Wikimedia projects in all languages, including Wikipedia, Wikivoyage, Wikisource, Wikiquote, Wiktionary, Wikinews, Wikibooks, and Wikispecies, or downloaded for offsite use. As of February 2023, the repository contains over 90 million free-to-use media files, managed and editable by registered volunteers.
